1. Field of the Invention
The present invention generally relates to the manufacture of polysilicon fuses in semiconductor devices and, more particularly, to a method of forming closely pitched polysilicon fuses which allows the density of fuses to be increased without the risk of damaging adjacent fuses when a fuse is blown.
2. Background Description
Crack stops are employed in silicon chip processing to reduce damage caused by chip dicing. A crack stop is typically a narrow trench etched down to the silicon substrate around the chip. A common method of forming the crack stop is to form a tungsten-filled trench around the chip, expose the tungsten (W) trench, and wet etch out the tungsten using hydrogen peroxide.
Fuse arrays are commonly formed in very large scale integrated (VLSI) circuits. The purpose of the fuses may be variously to customize the semiconductor device for a specific application or to disconnect a defective part of the device leaving a redundant part connected. The preferred manner of blowing a fuse is by laser ablation, but this creates a pit which limits how closely spaced fuses can be in the array to avoid damaging adjacent fuses.
It is known to use tungsten fuse barriers in aluminum/copper (AlCu) alloy fuses in order to protect adjacent fuses; however, tungsten fuse barriers are not compatible with the standard polysilicon fuse/crack stop process. This is because, in standard processing, the terminal via reactive ion etching (RIE) which thins the insulator above the polysilicon fuse also exposes the tungsten crack stop. If a tungsten fuse barrier were present, it would be removed when the tungsten crack stop was removed with the hydrogen peroxide etch.